Appalachian Fall Color August 6, 2017

It has been an unusually cool summer here in the High Country. Morning temperatures have been as low as 48F, and this past week, in the low 50s. We had to put on a blanket last night it got so cool! Daytime highs struggle to get in middle or high 70s. And the humidity has been low. Absolutely perfect weather.

Some trees have already decided that it’s time to prepare for the upcoming fall. The dogwood in my yard has already started turning purple. Note also on the whole tree photo (below) that the purpling is most noticeable on the left side of the tree – that’s the side that gets morning sun. My thought is that trees turn early on their east sides because that’s when they get the combination of both cool temperatures and high light. And those together can cause leaves to suffer photo-inhibition and cellular damage. By producing the purple pigment, which is an anthocyanin (the same compound that colors strawberries and roses) they protect their leaves from photo-inhibition. This in turn, allows them more time to withdraw nutrients, like nitrogen and phosphorus, back in to their leaves for use next year when they make new leaves.

Off the mountain, I’ve noticed that the tulip poplars have been losing a lot of leaves (they turn yellow then brown/black). According to the NC Climate Office, it has been a very hot summer in the Piedmont region of the state, and tulip poplars are sensitive to water stress, and maybe heat stress too. I haven’t seen the same leaf loss up here in the mountains. And we’re ahead in terms of rainfall this year.

Lastly, as happens every year at this time, the black locust are being attacked by the locust leaf miner, a native insect that eats the leaves and turns them brown. It doesn’t seem to hurt the trees too much, but does look bad as you drive down the road.